Abstract
In the context of climate change, chestnut fertilization is receiving great attention in the Mediterranean basin, due to the increase in the unpredictability of the pluviometric regime which makes it difficult to determine the optimal timing of fertilizer applications. The purpose of this work was to assess the suitability of fertilizers with mechanisms for nutrient protection on the increase of tree nutritional status and crop productivity. Four fertilizers with restricted nutrient solubility were tested: Bioscape 5:14:7 (32.8% organic matter (OM)); Humix 13:3:5 (80.1% OM); Exactyon AG 6:15:8 (37.7% N and 33.1% P encapsulated); and Exactyon AG 18:5:13 (47% N encapsulated, 28.8% N as urea coated with ammonium sulfate). The trials were carried out for four years in Moimenta and Meixedo, NE Portugal, which also received a non-fertilized control. In Moimenta the ground was managed by tillage and in Meixedo by a cover of natural vegetation. Exactyon AG 18:5:13, being the most concentrated in N and B, gave significantly higher cumulative (2015–2018) nut yields (146.6 kg tree−1) than the control (52.3 kg tree−1) in the Moimenta trial. The results were explained by the increase in leaf N and B levels, which in the control treatment were in the deficiency range. In Meixedo there were not found significant differences among treatments, likely due to the competition by cover crop for resources. The results showed that the response of the trees to the fertilizers relied mainly in their content in nutrients limiting to the agroecosystem and less in the mechanisms of nutrient protection.
Highlights
Chestnut (Castanea sativa Mill.) has gained remarkable importance in recent years for fruit production in some countries of the Mediterranean basin (Martins et al 2011; ÁlvarezÁlvarez et al 2010)
Among fertilized treatments no significant differences in nut yields were found, the highest average value was recorded in the trees treated with Exactyon AG 18:5:13
The fertilizer most concentrated in N and B and the one with the highest percentage of N protected gave higher leaf N and B concentrations and nut yield, which highlights the importance of N and B in these agroecosystems
Summary
Chestnut (Castanea sativa Mill.) has gained remarkable importance in recent years for fruit production in some countries of the Mediterranean basin (Martins et al 2011; ÁlvarezÁlvarez et al 2010). The recognition of the high nutritional value of the nuts and by-products (Borges et al 2008; Echegaray et al 2018) has raised the price of chestnut, which has led farmers to invest in the species. Chestnut trees are being planted just like other fruit tree species in true orchards and denser plantations (Martins et al 2011). There are few studies on chestnut fertilization, in comparison with the more widespread fruit species, those already done have highlighted the relevant role of B (Portela et al 2011, 2015; Arrobas et al 2017), K (Arrobas et al 2017), and N (Arrobas et al 2018) in the nutrition of chestnut trees
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